.TH LISTEN 1 "27 August 1996" Linux "Linux Programmer's Manual"
.SH NAME
listen \- monitor AX.25 traffic
.SH SYNOPSIS
.B listen [-8] [-a] [-c] [-h] [-i] [-p port] [-r] [-t] [-v]
.SH DESCRIPTION
.LP
.B Listen
uses SOCK_PACKET facilities to provide a network monitor of all AX.25
traffic heard by the system. Since KISS is implicitly promiscuous no
special driver configurations are needed.
.LP
This version displays standard AX.25, PE1CHL extended AX.25, NET/ROM, Rose, ARP,
IP, ICMP, TCP and UDP. It also displays IP, TCP, ICMP, TCP and UDP
encapsulated within NET/ROM frames. The program also displays AX.25 and IP
encapsulated within an IP frame, but see RFC1326 for reasons not to do so.
.LP
.B Listen
makes an attempt at decoding some of the more common routing protocols. RSPF
and RIP (both \(lqnormal\(rq and G8BPQs RIP98) are traced. JNOS style
NET/ROM node polls are also displayed.
.LP
.B Listen
can use colors to make the output more readable. The ncurses library is used
to accomplish this. 
.B Color support defaults to being disabled,
and the 
.BR -c
parameter is used to enable it.
.SH OPTIONS
.TP 10
.BI \-8
Indicates that the terminal is capable of printing 8-bit characters. This 
parameter is required for the -i parameter to work.
.TP 10
.BI \-a
Allow for the monitoring of outgoing frames as well as incoming ones.
.TP 10
.BI \-c
Enable color support.
.TP 10
.BI \-h
Dump the data portion of the packet in both hexadecimal and ASCII. The
default is to display data as ASCII only.
.TP 10
.BI \-i
Map IBM codepage 437 characters 128-158 to their ISO-Latin-1 equivalents.
This is a hack for scandinavian users. This parameter is only valid
when used with the -8 and -c parameters.
.TP 10
.BI "\-p port"
Monitor only those frames received on a particular port, by default all
AX.25 devices are monitored.
.TP 10
.BI \-r
Dump the data portion in a "readable" fashion, which is more suitable
for tracing plaintext AX.25 traffic. CR-LF conversion is done.
.TP 10
.BI \-t
Displays a timestamp with each packet received.
.TP 10
.BI \-v
Display the version.
.SH FILES
/etc/ax25/axports
.SH "SEE ALSO"
.BR call (1),
.BR mheard (1),
.BR beacon (1),
.BR ax25 (4),
.BR netrom (4),
.BR rose (4),
.BR kissattach (8).
.LP
.SH BUGS
.B Listen
does not validate the checksums of frames that support them (ie IP),
therefore corrupt frames will be displayed with bogus values. The MSS
of a TCP frame that contains that option is not displayed.
.SH AUTHORS
.nf
Alan Cox GW4PTS <alan@cymru.net>
.br
Jonathan Naylor G4KLX <g4klx@g4klx.demon.co.uk>
.br
Phil Karn KA9Q <karn@qualcomm.com>
.br
Heikki Hannikainen OH7LZB <hessu@pspt.fi>
.fi
